A rapid, inexpensive, non-lethal method for detecting disseminated neoplasia in a bivalve

Abstract

Disseminated neoplasia (DN) is a form of cancer in bivalve molluscs that has been reported in some cases to be a transmissible cancer. Neoplastic cells are highly proliferative, and infection is often lethal. Some commercially valuable bivalve species (mussels, cockles, soft-shell clams, oysters) are affected by outbreaks of disseminated neoplasia, making disease diagnosis and mitigation an important issue in aquaculture and ecological restoration efforts. Here we describe a minimally invasive, non-lethal method for high-throughput screening for disseminated neoplasia in basket cockles (Clinocardium nuttallii). Basket cockles are native to the North American Pacific coast from California to Alaska. There is recent concern from some Coast Salish Tribes regarding an observed long-term decline in cockle populations in Puget Sound, WA. This has led to increased interest in monitoring efforts and research to improve our understanding of the mechanisms of observed basket cockle population dynamics, including assessing prevalence of disease, such as disseminated neoplasia. The rapid, non-lethal hemolymph smear screening method presented here to diagnose DN in adult C. nuttallii can be applied at field sites at low financial cost, and in a validation study of 29 animals the results were identical to that of the gold standard method, tissue histology. Due to the similar morphology of DN in different bivalves, this method can likely be generally applied for use in any bivalve species.